1. Field of the Invention
The described embodiments relate to plate bending devices. More particularly, the described embodiment relates to pressing-bending machines that include a device for detecting the bending in the lower and upper cross-members.
2. Description of the Related Art
Pressing-bending machines are used in the metal and mechanical industry and, in particular, for sheet-plate working and manufacturing. Pressing-bending machines are used for the production of differently shaped longitudinal profiles in a piece of metal. Pressing-bending machines may optionally be capable of subjecting each sheet of metal to multiple bending cycles.
Generally, a bending cycle includes having a punch tool vertically descend onto a metal sheet-plate located on a matrix-die, bending the metal sheet-plate, and raising the punch tool up to the original position.
A pressing-bending machine may be made up of two elements. The two elements include a dynamic element, generally associated with the upper part of the machine, and a substantially static element known as the matrix support, associated with a lower part of the machine. The matrix support is placed vertically below the dynamic element.
In performing a bending cycle, a punch tool, including an interchangeable blade having a variety of shapes, is positioned in the dynamic element. The dynamic element vertically reciprocates the punch tool using at least two lubricated-dynamic cylinders. These cylinders typically control the descending, stopping, and rising of an upper cross-member of the dynamic element. The upper cross member longitudinally supports the punch tool.
The lower part of the pressing-bending machine includes a lower cross-member, which provides support for a matrix-die and measuring devices during use. French Patent No. 2,708,219 teaches a lower cross-member that may include devices for measuring and controlling the bending angle and deflection of the matrix-die at different points along the support matrix. Japanese Patent No. JP59193718 teaches maintaining the two dies in a parallel orientation. Japanese Patent No. JP8150416 teaches control of the respective deflection of the dies by use of detecting sensors. JP8150416 also teaches controlling the shape of the convex surface using a three-cylinder device to deflect the entire matrix portion. Japanese Patent No. JP4105714 teaches correction of central slack in the matrix when an environmental temperature is changed. JP4105714 further teaches that a lower die is slideably positioned between two guide plates. The lower die has a lower stroke sensor measuring the relative movement of the guide plates in relationship to a lower movable bending tool. The lower stroke sensor measurements allow correction of the lower bending tool acting with a lower counter cylinder. All these solutions teach detecting movement of the lower matrix or lower die with respect to the lower cross-member and the guide that supports it.
From a structural viewpoint, precision bending machines typically include a dynamic lower cross-member which allows the production of a high quality product. In contrast, machines that include a static lower member generally produce a lower quality product. The need to use machines which have a dynamic lower cross-member, is typically preferred by manufacturers. The costs for providing a dynamic lower cross-member, even if an optional one, are rather marginal with respect to the machine""s total cost.
One motivation for companies to use machines which have a dynamic lower cross-member is that the dynamic lower cross-member may help in correcting those imperfections; which cause a bending camber during the sheet-plate manufacture process.
The sheet-plate pressing-bending process may be difficult due to the required tolerances. A variety of factors may influence the accuracy of a sheet-plate manufacturing process. For example, changes in the thickness of a few centimeters in the sheet, in addition to the material quality of the sheet, may affect the accuracy of the sheet-plate manufacturing process. The elastic return of the material may also affect the accuracy of the sheet-plate manufacturing process. During the sheet-plate manufacturing process, the natural deformation of the two cross-members may also affect the accuracy of the process. The aforementioned factors are presently corrected by means of a computer controller that is coupled to the pressing-bending machine. The computer controllers may use suitable data, derived from previous tests and other manually operated systems that allow the controller to adjust the sheet-plate manufacturing process in a predetermined manner.
The deformation of the lower and upper cross-members of a pressing-bending machine is common to most pressing-bending machines. Such deformations during the processing of the sheet metal may be detected by noting a certain convexity or concavity along a transverse axis of the product. This xe2x80x9ccrowningxe2x80x9d or bending of the sheet metal may also be ascribed to the uneven force distribution on the upper cross-member cylinders.
Correction devices may be coupled to the bending machine to correct crowning or bending defects by allowing dynamic movement of the lower cross-member adjust for the intensity and distribution of the working pressure from the upper cross-member push cylinders. The dynamic movement of the lower cross-member may correct the bending camber caused by the bending strain on both cross-members. Typically, the bending camber is proportional to bending strain. The correction devices, though suitable for communicating with a computer controller of the bending machine, are typically not optimal because of a variety of factors, which reduce the correction device efficiency.
One factor for a reduction in efficiency may be that process corrections need continuous and special adjustments. These adjustments may not be singularly repeated, due to the changeable working conditions and the structural composition of the material used in manufacture. Changing working conditions may include the length of the piece to be bent, the thickness, the material""s maximum stress but primarily its longitudinal position in the pressing-bending machine where the bending operation may be carried out.
Hydraulic crowning systems of a press-bending machine typically includes a series of jacks, which may interact together at a lower intermediate section of an action cross-member. The action cross-member may be external to a corresponding reaction cross-member.
A frequent problem of a hydraulic crowning system may be that the deformation adjustment may be based on pre-set empirical parameters managed by a computer controller. Presently, the computer controller program variables may be obtained by sampling stages of repeated tests during normal and routine working conditions. The working conditions may correspond to a central positioning of a plate to be pressed-bent, and not to a final positioning of the plate in a cross-member. Pre-setting a suitable parameter may be difficult because of the different variables that influence the cross-members deformation during a work cycle. Specifically, the variables necessary for accurate correction of the cross-member deformation may be different from the routine working conditions.
Another definite lack of precision in the pressing-bending machines may be attributed to the absence of real data, supplied simultaneously with the pressing-bending operations. The real data may take into account the deformation, specifically, the bending or crowning of the cross-members. In addition, the lack of precision may influence the quality of the process by causing a considerable amount of scraps and/or may result in repeating a work cycle to correct an error.
A pressing-bending machine includes an upper cross member configured to support a punch. An upper fixed cross member is coupled to the upper cross member. The pressing-bending machine also includes a lower cross member positioned below the upper cross member. The lower cross member is configured to support a matrix-die. The lower cross member is composed of a lower action cross member, a first lower cross member guide, a second lower cross member guide, and a lower fixed cross member. The first and second lower cross member guides are positioned on opposing surfaces of the lower action cross member. The lower fixed cross member is coupled to the first lower cross member guide. The first and second lower cross member guides are independently movable with respect to each other. Detection devices are coupled to the upper and lower cross members. An upper detection device is coupled to the upper cross member. The upper detection device is configured to detect elastic deformation along a vertical axis of the upper cross member during use. The upper detection device includes at least one upper position transducer. The upper position transducer is coupled to the upper cross member. The upper position transducer includes a movable stem rod horizontally hinged to a pin. The pin is orthogonally coupled to the upper cross member through the upper fixed cross member. The stem rod of the upper position transducer is vertically movable with respect to the upper fixed cross member.
A lower detection device is coupled to the lower cross member. The lower detection device is configured to detect elastic deformation along a vertical axis of the lower cross member. The lower detection device includes at least one lower position transducer. The lower position transducer is coupled to the lower action cross member. The lower position transducer includes a movable stem rod horizontally hinged to a pin. The pin is orthogonally coupled to the lower action cross member through the lower fixed cross member and the first lower cross member guide. The stem rod of the lower position transducer is vertically movable with respect to the lower fixed cross member.
An upper control device is coupled to the upper cross member. The upper control device is configured to control elastic deformation along a vertical axis of the upper cross member. A lower control device is coupled to the lower cross member. The lower control device is configured to control elastic deformation along a vertical axis of the lower cross member.
Advantages are obtained which further improve existing pressing-bending machines. First, a hydraulic crowning system and a device for bending camber correction may include a system that may influence the intensity and distribution of the working pressure of a group of upper cross-member push cylinders. Specifically, the system may intervene more accurately than in other systems by taking into account the cross-members bending real values. As a consequence, obtaining high quality and precise results may be possible, independent of the material""s position with respect to the pressing-bending machine and material""s technical characteristics.
The end user may not need to perform any necessary adjustments, which may allow an essential faultless bending action. Press-bending cycle times may increase the economics of manufacture. The control device may allow improved working flexibility of the pressing-bending machine computer controller.